Mirror Backup setup and shows working, however looking for a file on the backups showed it to be missing, I installed and setup Synctoy which ran and copied over 5400 files it said were missing from the Mirror Backup. The Mirror Backup was run just before the SyncToy and shows all files backed up. The one folder is local and is mirroring to a shared drive on a 2nd machine on the network. Checking at 2 more locations (Companies) they have the same issue, synctoy finds thousands of files not mirrored. A manual check on random files from the list shows they are not on the mirror!!!

Just thought I would add they are all Data files, not using any plug ins, create full paths (inc drive letter) is UNTICKED, remove excluded or deleted files is Ticked, filters are SyncToy_*.*, it is also on a schedule but a manual run gives the same results.